Using Tuner to Determine Line Input Impedance
 

I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

Using Tuner to Determine Line Input Impedance
 

dykesc wrote:
I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

Wouldn't it be easier and much more accurate to make a known load out of
components close to what the MFJ-259B reads?

It also will be a frequency indepedant "calibration" if you keep the
component leads short.


--
Jim Pennino

Remove .spam.sux to reply.

Using Tuner to Determine Line Input Impedance
 

dykesc wrote:
I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

http://ytdp.ee.wits.ac.za/smithchart.pdf

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=8763

Using Tuner to Determine Line Input Impedance
 

On Jun 3, 1:15*pm, wrote:
dykesc wrote:
I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

Wouldn't it be easier and much more accurate to make a known load out of
components close to what the MFJ-259B reads?

It also will be a frequency indepedant "calibration" if you keep the
component leads short.

--
Jim Pennino

Remove .spam.sux to reply.

Jim,

I am concerned about an RF field from a local broadcast that may be
causing issues with using the low power MFJ 259B. When I use the auto
tuner I am tuning at 10 watts so plenty to counteract any local rf on
the antenna. I really need to back calculate an impedance from the
inductor, capacitor, and final swr from the auto tuner.

Using Tuner to Determine Line Input Impedance
 

dykesc wrote:
On Jun 3, 1:15Â*pm, wrote:
dykesc wrote:
I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

Wouldn't it be easier and much more accurate to make a known load out of
components close to what the MFJ-259B reads?

It also will be a frequency indepedant "calibration" if you keep the
component leads short.

--
Jim Pennino

Remove .spam.sux to reply.

Jim,

I am concerned about an RF field from a local broadcast that may be
causing issues with using the low power MFJ 259B. When I use the auto
tuner I am tuning at 10 watts so plenty to counteract any local rf on
the antenna. I really need to back calculate an impedance from the
inductor, capacitor, and final swr from the auto tuner.

OK, that's a different problem.

Have you concidered this if it is a general problem for you:

http://www.mfjenterprises.com/Produc...ductid=MFJ-731


--
Jim Pennino

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Using Tuner to Determine Line Input Impedance
 

dykesc wrote in news:22d6efc6-76ca-487a-9fc1-
:

....
I am concerned about an RF field from a local broadcast that may be
causing issues with using the low power MFJ 259B. When I use the auto
tuner I am tuning at 10 watts so plenty to counteract any local rf on
the antenna. I really need to back calculate an impedance from the
inductor, capacitor, and final swr from the auto tuner.

Why didn't you say that the first time?

Tom Rauch (one of the designers of the '259B) posted this info re
interference:

"BC interference causes the bridge in the analyzer to remian (sic)
unbalanced even with very low SWR, so the analyzer will read a fixed
minimum SWR when BC interference. It will read that way on any frequency
from dc to daylight. For example if the unit falls asleep the SWR meter
won't drop to zero. That's an indicator of BC interference or external
voltages being applied to the measurement port."

Owen

Using Tuner to Determine Line Input Impedance
 

On Jun 3, 4:19*pm, Owen Duffy wrote:
dykesc wrote in news:22d6efc6-76ca-487a-9fc1-
:

...

I am concerned about an RF field from a local broadcast that may be
causing issues with using the low power MFJ 259B. When I use the auto
tuner I am tuning at 10 watts so plenty to counteract any local rf on
the antenna. I really need to back calculate an impedance from the
inductor, capacitor, and final swr from the auto tuner.

Why didn't you say that the first time?

Guess I was in a hurry and just wanted to know if I could back
calculate the impedance (R +- jX) my auto tuner is seeing based on the
inductor, capacitor and final swr values it displays after a "match is
achieved. I would still like to do this. Dave gave me a link and of
course I can do it manually with a Smith Chart (I think lol).


Tom Rauch (one of the designers of the '259B) posted this info re
interference:

"BC interference causes the bridge in the analyzer to remian (sic)
unbalanced even with very low SWR, so the analyzer will read a fixed
minimum SWR when BC interference. It will read that way on any frequency
from dc to daylight. For example if the unit falls asleep the SWR meter
won't drop to zero. That's an indicator of BC interference or external
voltages being applied to the measurement port."

Owen

Thanks. Now there's a bit of info I didn't have. So if the 259B is
behaving normally, when it enters "battery save" mode the swr value
should drop to zero. If not, there are external voltages on the
antenna port. I think I will check this out with a 100 ohm resistor
across the antenna port. 2.0 should drop to 1.0 or zero when "battery
save" kicks in.

By the way, the broadcast station is FM at 105.5 MC.

Using Tuner to Determine Line Input Impedance
 

On Jun 3, 4:19*pm, Owen Duffy wrote:

Tom Rauch (one of the designers of the '259B) posted this info re
interference:

"BC interference causes the bridge in the analyzer to remian (sic)
unbalanced even with very low SWR, so the analyzer will read a fixed
minimum SWR when BC interference. It will read that way on any frequency
from dc to daylight. For example if the unit falls asleep the SWR meter
won't drop to zero. That's an indicator of BC interference or external
voltages being applied to the measurement port."

Owen

Many thanks Owen. I just confirmed I have a BC interference issue.
When I placed a 100 ohm resistor across the 259B antenna terminal, the
unit correctly read 2.0 (well actually 1.9) swr, 100 ohms R and 0 X.
When it entered "battery save" the analog swr and impedance meters
both dropped to zero. The digital display stayed the same.

When I hooked my antenna up the analog swr meter only fell to 1.4 when
the unit entered "battery save" mode. The impedance meter did drop to
zero. When I installed a 4:1 balun at the antenna feedpoint the swr
fell to 1.2, but still not zero when the analyzer entered sleep mode.
Apparently the BC signal is at least to some degree differential in
nature on my feedline.

Anticipating all this, I wrote MFJ about the usefullness of their
their tunable analyzer filter to combat a strong FM broadcast signal.
They replyed that it would work. I wonder how well. The tunable filter
costs around $100.00.

Using Tuner to Determine Line Input Impedance
 

On Wed, 3 Jun 2009 17:12:30 -0700 (PDT), dykesc
wrote:

costs around $100.00.

Drop a dime on a call to the station engineer and ask when they go off
the air for testing.

73's
Richard Clark, KB7QHC

Using Tuner to Determine Line Input Impedance
 

On Jun 3, 7:50*pm, Richard Clark wrote:

Drop a dime on a call to the station engineer and ask when they go off
the air for testing.

73's
Richard Clark, KB7QHC

Good idea Richard. I just sent them an e-mail. If I don't get a
response I'll call.

Thanks

Dykes AD5VS